Arlington County, VA Environmental Rules: Flood Elevation Requirements (2026)

Arlington County Code Chapter 48 sets the local floodplain elevation and construction standards that implement the National Flood Insurance Program. Under § 48-51(A), any new residential structure, or one undergoing substantial improvement, located in Zone AE or in a Zone A tract with a detailed Base Flood Elevation (BFE), must have its lowest floor, including any basement, elevated at least 18 inches above the base flood level. Section 48-51(B) applies the same 18-inch elevation floor to commercial, industrial and other non-residential buildings, but gives owners of AE and AO structures an alternative: dry floodproofing to at least two feet above the BFE, with all components below that line watertight and able to resist hydrostatic and hydrodynamic loads.

A registered professional engineer or architect must certify the floodproofing and file that certification, including the exact elevation reached, with the Floodplain Administrator. Section 48-51(C) governs enclosed space below the required elevation: it cannot be finished for living space, only for parking, building access or limited equipment storage, must use flood-resistant materials, and needs at least two engineered flood openings sized to one square inch per square foot of enclosed area. Accessory structures in the Special Flood Hazard Area are capped at 600 square feet under § 48-51(D); those between 560 and 600 square feet that cannot meet the elevation or floodproofing standards need a waiver before a permit issues, and none over 600 square feet qualify for a waiver at all.

Every application must include an Elevation Certificate documenting the lowest-floor elevation, required under § 48-57(B) and (D) before the Department of Environmental Services will issue a building permit.